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Aug2209
  Jimfromprovidence: <Eduardo Leon> <17. c5! Qa5 18. Bb5>
<I fail to see how blocking the e5 square with either knight prevents <19. c4>.
<18. ... Nce5 19. c6! Nxc6 20. c4>
<18. ... Nde5 19. c4 bxc5 20. f4>
The other possibility you mention can also be adequately refuted:
<18. ... f6 19. cxd6 cxd6 20. c4>> Your analysis is interesting.
My point was that there are plenty of options to work through in this 17 c5! Qa5 18. Bb5 line, knowing that black has better options than having to castle or play 18…a6 or 18…Rg8 in this continuation. In your first line for example, <18. ... Nce5 19. c6! Nxc6 20. c4> black does not have to play 19…Nxc6 but has 19…Nd5. If white follows with 20 c4 black has 20…a6 or 20…Bxd5. White has an advantage but it is a very deep position. 

Aug2209
  johnlspouge: < <JimFromProvidence> wrote: [snip] In summary, all these lines seem incredibly difficult to follow. > Because I try to "prove" the candidate puzzle move wins, I have developed methods to abbreviate my (longwinded and tedious) posts. The best method is to state the threat after (e.g.) White makes each of his moves. The analysis can then omit moves that do not meet the threat. By my convention, Black's later moves must all meet the threat. Today, some kibitzers repeat the threat of trapping Qa4 in several variations, making the lines "incredibly difficult to follow." Black can always play his responses to a threat one move early, but in my implicit conventions, if White just plays the corresponding move from the threat, the threat remains in force. My post considered responses to the candidate 17.c5 like Black's N moves, but they eventually transpose into the threat, or obviously lose material. The convention of stating the threat prunes the decision tree drastically, which speeds calculation in any situation where time is precious (such as over the board, or indeed, in life itself). 

Aug2209   WiseWizard: not only does it win material, the move is an excellent strategic decision because Black closes the c file and Whites's weak c pawn and file can breath a little. It also takes aggressive measure to avoid the nightmare of a knight on c4 where black would achieve a positional plus. Instructive play Portisch. 

Aug2209
  johnlspouge: < <Athamas> wrote: [snip] 17. c5 Qa5 18. Bb5 Nxc5 19. c4 Rg8 [snip] > The variation is essentially transposes the basic threat after the immediate response 17...Nxc5 (which I gave). Kotov's Rule (a P advantage terminates analysis) speeds calculation, particular if suboptimal variations are permitted. In several previous puzzles, suboptimal variations have followed a comprehensible human "logic" better than best play. (Today, e.g., I do not know if the variation I gave against 17...Nxc5 is best play.) 

Aug2209   David2009: Saturday's puzzle Portisch vs A Deze, 1971 White to play 17? Very difficult There are no obvious forcing moves. I can play positionally to undouble my Pawns, e.g. 17 Bd4 Nxd4 18 cxd4 but White has no advantage. The Black Q is short of squares, so 17 c5 is possible. The Pawn can be captured in three ways: (a) If 17... bxc5 18 Bb5 Qa5 19 c4 Rg8 20 Bd2 and 20... Qd8 is forced. 17... bxc5 18 Bb5 Rb8 doesn't work: the Nc6 is en prise after the Queens come off. (b) 17... dxc5 is similar to line (a) but much worse for Black since the Queen is trapped. (c) 17... Nxc5 18 Bb5 Qa4 19 c4 Rg8 20 Bd2 traps the Queen. Conclusion: Black must play line (a). In exchange for the Pawn at c3 Black's pieces have been driven to very passive squares, and White can build up on the b file. Time to check. ========
I got the first two moves but not the stunning 19 Bxc6!! followed by
Qb7 winning everything. The unlucky Rook can't move anywhere sensible, neither can the Queen protect it. I wonder if Anton Deze was as surprised as I was when 19 Bxc6 was played instead of 19 c4. Time to digest other comments and the full game. 

Aug2209   wals: [Event "Vrsac"]
[Site "Vrsac"]
[Date "1971.??.??"]
[Round "?"]
[White "Lajos Portisch"]
[Black "Anton Deze"]
[Result "10"]
[ECO "A30"]
[Annotator "Rybka 3 1cpu (30m)"]
[PlyCount "39"]
{B37: Sicilian: Maroczy Bind
1. c4 c5 2. d4 g6 3. Nf3
cxd4 4. Nxd4 Nc6 5. e4 Nf6 6. Nc3 d6 7. Nc2 Bg7 8. Be2 Nd7 9. Be3 Bxc3+ 10.
bxc3 Qa5 11. Qd2 Nc5 12. f3 Qa4 13. OO Be6 ♗lack threatens to win material:
♗e6xc4 (13... OO 14. Nb4 ) 14. Nb4 (14. Rab1 OO (14... Qxa2 the
pawn must be left alone, otherwise ♗lack will be punished 15. Bxc5 Na5 16. Bd4
)) 14... Rc8 (14... OO 15. Nd5 ) 15. Nd5 (15. Bxc5 dxc5 16. Nd5 )
15... Nd7 (15... OO 16. h4 ) 16. Qb2 (16. Rab1 b6 17. c5 bxc5 18. Rb7
) 16... b6 ? ♙revents intrusion on c5 (16... f6 17. c5 (17. Qxb7
Rb8 18. Bd1 Qxc4 (18... Rxb7 19. Bxa4 Na5 20. Rfb1 )) 17...
Nxc5 18. Bxc5 dxc5 19. Qxb7 ) 17. c5 bxc5 ?? (17... Nxc5 18. Bb5
Qa5 ) 18. Bb5 Qa5 (18... Rb8 19. Bxa4 Rxb2 20. Bxc6 Bxd5 21. exd5 )
19. Bxc6 Rxc6 (19... Qd8 is not the saving move 20. Qb5 OO 21. Bh6 ) 20.
Qb7 (20. Qb7 f6 21. Qxc6 ) 10
The above may be of interest to those needing help. 

Aug2209   David2009: After 17 c5! 17...Nxc5 is a very good try. Queen trapping is harder than it looks: <TheBish: [snip] D) 17...Nxc5 18. Bb5! Qa5 19. c4 f6 20. Bd2 Nd3 21. Qc2 Qa3 22. Rab1 Qc5+ 23. Be3 Qa3 24. Rb3 Qa5 25. Bd2! traps and wins the queen.>
Crafty plays 17...Nxc5 18 Bb5 Qa5 19 c4 Rf8 20 Bd2 Nd3 21 Qc2 Qa3 22 Rab1 Nc5! and if 23 Bb4 Qe6, or if 23 Rfe1 Kd8. <OBIT [snip] Simpler is 20. a3! trapping the queen without all the fuss.> Exactly. Continuing with <OBIT>'s suggestion gives 20 a3! Nd3 21 Qc2 Kd8 22 Qxd3 Ne5 23 Qe2 Bxd5 24 cxd5
and extricating the Queen has cost Crafty a piece.
http://www.chessvideos.tv/endgamet... 

Aug2209
  johnlspouge: < <David2009> wrote: <OBIT [snip] Simpler is 20. a3! trapping the queen without all the fuss.> Exactly. Continuing with <OBIT>'s suggestion gives 20 a3! Nd3 21 Qc2 Kd8 22 Qxd3 Ne5 23 Qe2 Bxd5 24 cxd5 and extricating the Queen has cost Crafty a piece. > Hi, <David2009>. Thanks. I missed 20...Nd3, so I underestimated 17...Nxc5. Your variation also indicates nicely how an "inferior" variation can be both simple and sufficient to win. 

Aug2209   RandomVisitor: After 17.c5!
1: Lajos Portisch  Anton Deze, Vrsac 1971
click for larger viewAnalysis by Rybka 3 : (top 4 lines 20ply, the rest 19ply) 1. (2.86): 17...Nce5 18.Bb5 Qa5 19.c4 bxc5 20.Bd2 Qd8 21.f4 00 22.fxe5 Nxe5 23.Bh6 Rb8 24.Bxf8 Qxf8 25.Qa3 Qd8 26.Rab1 Rb7 27.Ba6 Rxb1 28.Rxb1 Bd7 29.Qb2 Kg7 30.Rf1 Bc6 31.Bb5 Bxd5 32.exd5 Qa5 2. (2.87): 17...Qa5 18.Bb5 Bxd5 19.c4 00 20.cxd5 Nce5 21.Bd2 Nc4 22.Bxa5 Nxb2 23.Bxd7 Rxc5 24.Bd2 Rd8 25.Bc6 Rc2 26.Bh6 f6 27.Rac1 Rxc1 28.Rxc1 Nd3 29.Rc3 Nc5 30.Ra3 a5 31.Be3 Rc8 32.Rc3 e5 3. (2.89): 17...Bxd5 18.Bb5 Qa5 19.c4 00 20.cxd5 Nce5 21.Bd2 Nc4 22.Bxa5 Nxb2 23.Bxd7 Rxc5 24.Bd2 Rd8 25.Bc6 Nd3 26.a4 Rc2 27.Be3 Rb8 28.Bb5 Nc5 4. (2.95): 17...a6 18.c4 f6 19.cxd6 Kf7 20.dxe7 Nxe7 21.Rac1 Rhe8 22.Bd4 Bxd5 23.cxd5 Rxc1 24.Rxc1 Rc8 25.Bf2 g5 26.Rxc8 Nxc8 27.Qc3 Nd6 28.Qc7 Ne8 29.Qa7 Nd6 30.Qxa6 Qxa6 31.Bxa6 b5 32.Be1 Nb8 5. (2.98): 17...Na5 18.cxd6 Bxd5 19.exd5 Nc4 20.Bxc4 Qxc4 21.dxe7 f6 22.d6 Qxc3 23.Qe2 Qc2 24.Qa6 Qc4 25.Qxa7 Qd3 26.Rfe1 Qxd6 27.Rad1 Qc7 28.Qa4 Qc6 29.Qb4 Qc3 30.Qh4 Qc6 31.Bf2 Kf7 32.Qf4 6. (2.99): 17...f6 18.Bb5 Qa5 19.c4 bxc5 20.Bxc6 Qd8 21.Qb7 Kf7 22.f4 Nb6 23.f5 Bd7 24.Nxb6 Bxc6 25.Qxc8 Qxc8 26.Nxc8 Rxc8 27.fxg6+ Kxg6 28.Rf4 Rb8 

Aug2209   WhiteRook48: missed it 

Aug2209   LIFE Master AJ: Saturday; August 22nd, 2009.
White to move, (17. '?').
click for larger viewPortisch vs A Deze, 1971 (Kostic Memorial in Vrsac, Yugoslavia.) First of all, you should read the posts of "all the usual suspects." (<dzechiel>, <thebish>, <once>, <agb2002>, etc. Also, <"RandomVisitor"> has a good RYBKA analysis of just about all the main lines here.) I consider it a waste of time to repeat most of what has already been stated. Secondly, I found this one easy ... at least compared to the madness of Beliavsky vs. Gulko. (Yesterday's puzzle.) Today, I was teaching my chess student (John Laning), so I printed out the diagram and we set it up on my chessboard. I saw ... almost instantly ... the possibility of the "clearance move" of 17.c4c5! I very quickly worked out one line ... NOT saying that these moves are the machine moves (or best), JUST WHAT I SAW OTB: 17...dxc5; 18.Bb5 Qa5; 19.c4 f6; '▢' (Much worse was: </= 19...00?; 20.Bxc6 Rxc6; 21.Nxe7#.) 20.Bd2 Nb4; 21.a3 Nd3; 22.Qc2 Nb4; 23.axb4, and White is winning the BQ, " " I quickly worked out a few other variations, including what was played in the game. BTW, my student gave the following line, claiming it was better for White. < 17.♕b3 ♘c5; 18.♗xc5 ♕xb3; 19.axb3 dxc5; 20.f4, " "> Turns out he was right! 

Aug2309
  OBIT: <David2009>To give credit where credit is due, it was <Old Wolf> who first pointed out 20. a3! in the 17...Nxc5 continuation. After 20. a3, your computer suggests Nd3 21 Qc2 Kd8 to at least save the queen at the cost of a piece. I was surprised to find out the queen can still escape after 22. Bd2, but apparently this is true: 22. Bd2 Ncb4 23. axb4 and now 23...Qxb5!? keeps the queen on the board, although after 24. Qxd3 I can't see White haven't any trouble winning this. Another possibility is 23...Nxb4, but here even better than 24. Bxb4 is 24. Nxb4!, to meet 24...Qxb5 by 25. cxb5 Rxc2 26. Nxc2. 

Aug2609   LIFE Master AJ: <OBIT> I saw the idea of a3  in several lines  although I wound up abbreviating my post. 

Oct2210   arecely63: this game could have been played with 1.e4 c5 and then you would call it a sicilian. Probably lots of similar stuff to look up in B37/4 for opening study.(IT IS INFORMANT GAME 13/370) 

Mar1420   Cheapo by the Dozen: The first unblocking move was obvious, both for what it opened on the queenside  especially given the precarious position of Black's queen  and perhaps for the a1h8 diagonal as well. But in my brief look at the puzzle I absolutely didn't see the Qb2 idea for followup. 

Mar1420   Walter Glattke: Several other win possibilities, e.g. 17.c5 bxc5 18.Bb5 Qa5 19.c4 f6 20.Bxc6 Rxc6 21.Qb7 Bxd5 22.exd5 Rd6 23.Bf4 e5
24.dxe6 e.p. Rxe6 25.Bc7 Qb4 26.Qa8+ Kf7 27.Qxh8 very difficult? Absolutely not, too many win ways. 

Mar1420
  al wazir: I found 17. c5 because I saw that the black ♕ might be trappable, but I went astray, completely missing the winning mate: 17. c5 bxc5 18. Bb5 Qa5 19. c4, threatening 20. Qxh8. But black can easily defend with 19...f6. (Not 19...OO 20. Bxc6 Rxc6
21. Nxe7#.) 

Mar1420   stacase: I got 17.c5 & 8.Bb5 and didn't see the rest. Like <al wazir> I was thinking about <trapping> or in some way neutralizing whatever Black's Queen was up to. 

Mar1420
  thegoodanarchist: These puzzles late in the week help me to understand my chess ability. All those tactical puzzles over the decades really paid off well. I can see the lines and calculate them. I almost always find that, when I check the solution, it is one of the lines I analyzed in my mind. My problem is, evaluation of the resulting position! After calculating out to 18...Qa5, I could see, in my mind's eye, that 19.Bxc6 Rxc6 was possible, weakening the black back rank. But I didn't judge that as winning for white! Portisch did, and he played only 1 more move before his opponent gave up. Positional evaluation. That's the weakest part of my game. It is why I didn't earn a title. 

Mar1420   JohnBoy: It never ceases to amaze me that software and silicon can calculate a bajillion lines at 20 ply in a second or two. Nothing escapes these monsters. 

Mar1420
  agb2002: White has the bishop pair for a bishop and a knight. The black queen lacks mobility and both rooks are defenseless. These details suggest 17.c5: A) 17... Bxd5 18.Bb5 Qa5 19.c4 Rg8 (19... Nde5 20.f4 wins a piece at least) 20.Bd2 wins decisive material. B) 17... dxc5 18.Bb5 Qa5 19.c4 Rg8 20.Bd2 Nb4 21.a3 wins decisive material. C) 17... Nxc5 18.Bb5 Qa5 19.c4 Rg8 20.Bd2 Nd3 (20... Na4 21.Qc2 wins decisive material) 21.Qc2 Qa3 22.Bc3 Nc5 (22... Ndb4 23.Bxb4 wins) 23.Bb4 wins decisive material. D) 17... bxc5 18.Bb5 Qa5 (18... Rb8 19.Bxa4 Rxb2 20.Nc7+ Kd(f)8 21.Nxe6+ fxe6 22.Bxc6 wins a piece) 19.Bxc6 Rxc6 20.Qb7 D.1) 20... Q(R)a6 21.Nc7+ wins an exchange at least. D.2) 20... Qa4 21.Qa8+ wins a piece at least.
D.3) 20... Ne5 21.Qxe7#.
E) 17... 00 18.Bb5 Qa5 19.Bxc6 Rxc6 20.Nxe7+ wins a rook. F) 17... a6 18.cxb6 wins an important pawn.
G) 17... Ncb8 18.Bb5 as above. 

Mar1420
  perfidious: <JohnBoy.....Nothing escapes these monsters.> I'll sign that.
And Miles thought Kasparov was a 'monster with a hundred eyes'.... 

Mar1420
  chrisowen: Torvil and Dean no? 

Mar1420   RandomVisitor: A modern look at the position after 17.c5!, and 10.5 years after my previous attempt: click for larger viewStockfish_20030407_x64_modern:
46/78 3:24:47 +4.71 17...a6 18.cxb6 Bxd5 19.exd5 Ncb8 20.c4 f6 21.Rfe1 00 22.Rab1 Kg7 23.b7 Rc7 24.f4 Nc5 25.Bxc5 Rxc5 26.Bd3 Rc7 27.g4 Kg8 28.h4 a5 29.Kh1 Qb4 30.Qe2 Qc3 31.f5 g5 32.hxg5 fxg5 33.Qe3 Kh8 34.Kg2 Qf6 35.Qd2 a4 36.Re4 Kg8 46/68 3:24:47 +5.47 17...Qa5 18.Bb5 Nxc5 19.c4 f6 20.Rfd1 a6 21.Bd2 Nd3 22.Qb3 Nc5 23.Qe3 axb5 24.Bxa5 Nxa5 25.cxb5 Bxd5 26.exd5 h5 27.Re1 Rh7 28.Rac1 Kd7 29.h4 Nab7 30.Rc3 Kc7 31.Qd2 Rg7 32.Ree3 Re8 33.Re2 Kd7 34.Qf4 Rh8 35.Kh2 Kc7 36.Rce3 Rhh7 46/72 3:24:47 +5.47 17...bxc5 18.Bb5 Rb8 19.Bxa4 Rxb2 20.Bxc6 Kd8 21.Rab1 Bxd5 22.exd5 Rb6 23.c4 e6 24.Bd2 Ke7 25.dxe6 Ne5 26.Rxb6 axb6 27.Bc3 Rc8 28.Be4 Kxe6 29.Bd5+ Kd7 30.f4 Nc6 31.f5 Ne7 32.fxg6 Nxd5 33.Rxf7+ Ke8 34.cxd5 hxg6 35.Rb7 Ra8 36.Rxb6 Kd7 46/65 3:24:47 +5.49 17...Bxd5 18.Bb5 Qc4 19.cxd6 e5 20.Bxc4 Bxc4 21.Bh6 f6 22.Qc2 Rg8 23.f4 exf4 24.Qa4 Be6 25.Bxf4 Kf7 26.e5 f5 27.Be3 h5 28.Bd4 h4 29.Qd1 Rh8 30.Qd3 Rh5 31.Qa6 Rhh8 32.Rae1 Kg7 33.Qd3 Rb8 34.Re2 Rbc8 35.Qe3 Rh5 36.Rfe1 g5 46/68 3:24:47 +5.61 17...Nxc5 18.Bb5 Qa5 19.c4 f6 20.Rfd1 a6 21.Bd2 Nd3 22.Qb3 Nc5 23.Qe3 axb5 24.Bxa5 Nxa5 25.cxb5 Bxd5 26.exd5 h5 27.Re1 Rh7 28.Rac1 Nab7 29.Qa3 Na5 30.h4 Kd7 31.Qe3 Nab7 32.Rc3 Kc7 33.Qf4 Kb8 34.Rce3 Re8 35.Rc1 Rg8 36.Qd4 Rhg7 46/85 3:24:47 +5.85 17...Nce5 18.Bb5 Qa5 19.c4 bxc5 20.f4 Bxd5 21.fxe5 Bc6 22.e6 f6 23.exd7+ Bxd7 24.a4 a6 25.e5 dxe5 26.Bxd7+ Kxd7 27.Qb7+ Qc7 28.Qxa6 Qc6 29.Qb5 Ke6 30.a5 Rc7 31.a6 Ra8 32.Qxc6+ Rxc6 33.a7 Rc7 34.Ra6+ Kd7 35.Rfa1 e4 36.R6a5 Kc8 46/76 3:24:47 +6.27 17...f6 18.Bb5 Qa5 19.cxd6 Kf7 20.dxe7 a6 21.a4 Nce5 22.e8R Rhxe8 23.Bxb6 Nxb6 24.Bxe8+ Kxe8 25.Qxb6 Qxb6+ 26.Nxb6 Rc7 27.Rfb1 Kf7 28.Nd5 Ra7 29.Rd1 a5 30.Rab1 Nc4 31.Rd4 Ne5 32.Rb5 Bd7 33.Rb6 Be6 34.Kf2 Nd7 35.Rb5 Nf8 36.Nb6 Nd7 46/71 3:24:47 +6.41 17...Na5 18.Bb5 Nc4 19.Qb1 Qa5 20.Bxc4 Bxd5 21.exd5 Rxc5 22.Qb3 Rc7 23.Bb5 00 24.c4 Nc5 25.Qc2 Qa3 26.Bh6 a6 27.Bxf8 Kxf8 28.Bc6 Nd3 29.Rab1 Rc8 30.Qd2 Ne5 31.Rxb6 Qc5+ 32.Qf2 Qxc4 33.Rfb1 Kg7 34.Qe3 Qxa2 35.Qd4 Qc4 36.Qxc4 Nxc4 45/81 3:24:47 +7.89 17...Nde5 18.Bb5 Nc4 19.Qb1 Qa5 20.Bxc4 bxc5 21.Bb5 f6 22.Bxc6+ Rxc6 23.Qb7 Bd7 24.e5 dxe5 25.Rfd1 Qd8 26.Qxa7 Kf7 27.Bxc5 Re8 28.Nxf6 Kxf6 29.Rxd7 Qa8 30.Bxe7+ Ke6 31.Bb4 Qxa7+ 32.Rxa7 e4 33.fxe4 Rcc8 34.Rxh7 Rc4 35.Rf1 Ke5 36.Rh4 Ra8 45/79 3:24:47 +8.34 17...Nf6 18.Nxf6+ exf6 19.Bb5 Qa5 20.c4 bxc5 21.Qxf6 Rf8 22.Bg5 Qd8 23.Bxc6+ Bd7 24.Bxd7+ Kxd7 25.Qxd8+ Rfxd8 26.Bxd8 Rxd8 27.Rab1 Ke6 28.Rb7 a5 29.Rfb1 g5 30.Ra7 h5 31.Rd1 g4 32.Rxa5 gxf3 33.gxf3 h4 34.Ra6 Ke7 35.Rd5 Rg8+ 36.Kf2 h3 

Mar1420   takchess: Portisch vs A Deze, 1971
17.
Need to study this one 



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